The present invention relates to a friction mechanism for control apparatuses. More specifically, it relates to a friction mechanism for a control lever in a single-lever-type control apparatus for controlling engines in small vessels and the like.
The control lever in a control apparatus operates the clutch and accelerator through a control cable. A control lever is generally operated as follows. The neutral position is in the center. Inclining the lever forward shifts the clutch into forward, and moving the lever farther ahead opens the accelerator throttle valve. Conversely, moving the lever backward from the neutral position shifts the clutch into reverse, and moving it farther back opens the throttle valve.
Fine accelerator adjustments are difficult and it is dangerous when the control lever can be inclined under too little force during accelerator manipulation. Resistance during lever movement becomes unstable because it is governed mainly by engine parts, frictional resistance of rotating parts in the control apparatus, sliding friction on the control cable and the like. This instability complicates accelerator adjustment.
Thus, friction mechanisms for applying a virtually uniform resistance to the control lever are provided in the prior art in order to obtain a consistently stable response.
For example, in control apparatus 51 in FIG. 6, the base of the control lever 52 and a discoidal accelerator wheel 54, housed in a wheel case 53, are connected through a shaft 55 which is concentric to the accelerator wheel 54.
A gear 57 connected to a linking mechanism (not pictured) for pushing and pulling the control cable 56 and plural concavities 58 which constitute a detent mechanism are formed in one region of the outer circumference of the accelerator wheel 54 (see FIG. 7).
The following friction mechanism is also provided. Here, friction block 59 in the above wheel case 53 is pressed against the side surface 54a of the accelerator wheel 54 by screw 60, provided parallel to the axis of the accelerator wheel 54. Friction is thereby applied against the rotation of the accelerator wheel 54, and, as a result, a uniform resistance can be applied against inclinations of the control lever 52.
Low frictional resistance is generally a problem of the prior art friction mechanisms. In order to apply strong resistance, friction block 59 must be large, but the size of the friction block 59 is limited by the gear 57 on accelerator wheel 54 and by the concavities 58.
Furthermore, because of mounting space limitations, the prior art friction mechanisms are constructed in such a way that the screw 60, positioned axially to the accelerator wheel 54, applies pressure, through the friction block 59, to only a single point on the side 54a of the accelerator wheel 54. Consequently, if there is any play in the direction in which this pressure is applied, the wheel 54 tilts, causing both a poor response and control failures.